How to scale and move a mesh to specific location and axis in Blender 2.8
Welcome to Blender Stack exchange! It appears that you are in edit mode and want to move the shorter plane near to the larger one(as described). You can just select the plane and move it using G hotkey, but make sure you are not selecting anything else other than the plane. You can go into edit mode > deselect everything (Double tap A or Alt A) > hover over the plane you want to move > press L to select that plane > use the move tool to move in the choice of your direction. I would recommend you to see some videos of Blender Guru, CGGeek, CGCookie to get started with blender.